Putin Phones Obama To Discuss Ukraine, White House Says

Russian president Vladimir Putin called President Barack Obama Friday to discuss a U.S.-proposed diplomatic solution to the ongoing crisis in Ukraine, the White House said in a statement.

Obama asked that Russia provide a written response and the presidents agreed that their respective foreign ministers would discuss what comes next, the White House said.

The call between the two leaders comes amid high tensions following Russia’s annexation of the southern region of Crimea last week. Russia has amassed some 50,000 troops along Ukraine’s eastern border that it says are involved in military exercises, but U.S. officials have expressed concern that they could be used for another Russian landgrab.

Earlier Friday, Obama told CBS News that Russia should stop "intimidating" Ukraine and pull its troops back to "de-escalate the situation."

Secretary of State John Kerry met with his counterpart Sergei Lavrov earlier this week on the sidelines of a nuclear summit at The Hague and presented him the proposal for de-escalation of the showdown that has seen reciprocal economic sanctions and a flurry of Cold War-style rhetoric from both sides.

During the conversation, Obama told Putin a diplomatic solution "remains possible only if Russia pulls back its troops and does not take any steps to further violate Ukraine’s territorial integrity and sovereignty,” according to the White House. "President Obama reiterated that the United States has strongly opposed the actions that Russia has already taken to violate Ukraine's sovereignty and territorial integrity."